The present application relates to an optical measuring device for optically detecting samples such as minute particles or the like, and particularly to techniques of irradiating samples flowing within a channel and detecting light emitted from the samples.
An optical measuring device such as a flow cytometer or the like is generally used to identify living body related minute particles such as cells, microorganisms, liposomes and the like (see “Cellular Engineering Extra Number Experiment Protocol Series Flow Cytometry at Will,” Second Edition, Shujunsha Co. Ltd., issued on Aug. 31, 2006, edited by Hiromitsu Nakauchi for example). The flow cytometer is a device that identifies a plurality of minute particles one by one by irradiating the minute particles flowing in a line within a channel with laser light of a specific wavelength and detecting fluorescence or scattered light emitted from each minute particle.
Specifically, in a flow cell, a laminar flow is formed by a sample liquid including minute particles to be measured and a sheath liquid flowing on the periphery of the sample liquid, and a slight pressure difference is produced between the sample liquid and the sheath liquid, whereby the plurality of minute particles included in the sample liquid are arranged in a line. When the flow cell is irradiated with laser light in this state, the minute particles pass the laser light so as to traverse the laser beam one by one. At this time, fluorescence and/or scattered light excited by the laser light and emitted from each minute particle is detected by using an electrooptic detector.
In addition, there is a method of using a substrate having a fine channel formed therein in place of a flow cell (see Japanese Patent Laid-Open Nos. 2003-302330 and 2004-85323 hereinafter be referred to as Patent Documents 1 and 2, for example). Existing microchips described in Patent Documents 1 and 2 have one or a plurality of channels through which to make samples to be measured flow in a transparent substrate. For example, two sheath liquid introducing channels join a sample liquid introducing channel from both sides to form one sample channel, and a laminar flow is formed at the junction part of these channels.
Another existing microchip has been proposed which has a reference channel through which to make a liquid including no samples flow in addition to a channel through which to make a sample liquid including samples to be measured flow in order to improve detection accuracy (see Japanese Patent Laid-Open No. 2003-4752 hereinafter be referred to as Patent Document 3). FIG. 13 is a plan view of a channel constitution of the existing microchip described in Patent Document 3. As shown in FIG. 13, the microchip 100 described in Patent Document 3 has a specimen introducing opening 102 for introducing a specimen such as blood or the like on a substrate 101, and has specimen channels 103a to 103c and a reference channel 104 connected to the specimen introducing opening 102. Of these channels, the specimen channels 103a to 103c are joined by reagent channels 105a to 105c through which to make a reagent to react with the specimen flow to form merged channels 106a to 106c. In addition, a detecting section 107 is provided for each of the merged channels 106a to 106c and the reference channel 104.
When measurement is made using the above-described microchip 100, a specimen such as blood or the like is supplied from the specimen introducing opening 102, so that the specimen is made to flow through the specimen channels 103a to 103c and the reference channel 104. In addition, a reagent to react with the specimen is made to flow through the reagent channels 105a to 105c, so that the specimen and the reagent react with each other in the merged channels 106a to 106c. Then, the detecting section 107 irradiates the respective liquids flowing through the merged channels 106a to 106c and the reference channel 104 with light, and detects scattered light or reflected light emitted as a result of the irradiation.
In the microchip 100 described in Patent Document 3, the reference channel 104 is not joined by a reagent channel, and thus the unreacted specimen flows through the reference channel 104. Thus, a signal detected from the reference channel 104 corresponds to a noise component of signals detected from the merged channels 106a to 106c. Only a signal originating from the reaction with the reagent can be obtained by performing signal processing that subtracts the detection signal from the reference channel 104 from the detection signals from the merged channels 106a to 106c. 